Many different things can make kids throw up, including illnesses, motion sickness, stress, and other problems. In most cases, though, vomiting in children is caused by gastroenteritis, an infection of the digestive tract.

Gastroenteritis, often called the "stomach flu," usually is caused by common viruses that we come into contact with every day. Besides causing vomiting, it also can cause nausea and diarrhea.

Gastroenteritis infections usually don't last long and are more disruptive than dangerous. But kids (especially infants) who cannot take in enough fluids and also have diarrhea could become dehydrated, meaning that their bodies lose nutrients and water, leading to further illness.

It's important to stay calm — vomiting is frightening to young children (and parents, too) and exhausting for kids of all ages. Reassuring your child and preventing dehydration are key for a quick recovery.

Giving kids the right fluids at the right time (called "oral rehydration") is the best way to help prevent dehydration or treat mild fluid loss.

What Is Oral Rehydration?

When fluids are lost through vomiting or diarrhea, it's important to replace them as soon as possible. The key is drinking small amounts of liquid often to replace water and nutrients that have been lost.

The best liquids for this are oral rehydration solutions — often called oral electrolyte solutions or oral electrolyte maintenance solutions. They have the right balance of fluids and minerals to replace those lost to vomiting and help kids stay hydrated.

Most electrolyte solutions are available at supermarkets or drugstores. If you think your child is at risk for dehydration, call your doctor. He or she might have specific oral rehydration instructions and can advise you on which solution is best for your child.

Note: Over-the-counter medicines to treat nausea, vomiting, and diarrhea are not recommended for babies and children. In certain situations, doctors might recommend medications for nausea or vomiting but these are available only by prescription.

Rehydration Tips: Babies (Birth to 12 Months)

Do not give plain water to an infant unless your doctor tells you to and specifies an amount. Plain water by itself can disrupt the balance of nutrients in your baby's blood.

If your baby is younger than 2 months old and vomits (not just spits up, but vomits what seems like an entire feeding) at ALL feedings, call your doctor immediately.

For Breastfed Babies

If your infant is exclusively breastfeeding and vomits (not just spits up, but vomits what seems like the entire feeding) more than once, breastfeed for shorter periods of time (about 5 to 10 minutes at a time) every 2 hours. Increase the amount of time your baby feeds as he or she is able to tolerate it. If your baby is still vomiting on this schedule, call your doctor. After about 8 hours without vomiting, you can go back to your normal breastfeeding schedule.

For Formula-fed Babies

Offer small but frequent amounts — about 2 teaspoons (10 milliliters) — of an unflavored oral electrolyte solution every 15-20 minutes with a spoon or an oral syringe. Check with your doctor about which type of solution is best.

A baby over 6 months old may not like the taste of a plain oral electrolyte solution. You can buy flavored solutions, or (only for babies over 6 months) you can add ½ teaspoon (about 3 milliliters) of juice to each feeding of unflavored oral electrolyte solution.

If your baby can keep an electrolyte solution down for more than a couple of hours without vomiting, gradually increase the amount you give. For instance, if your little one normally drinks 4 ounces (about 120 milliliters) per feeding, slowly work up to giving this amount of oral electrolyte solution as the day goes on.

Sometimes very thirsty babies will try to drink a lot of liquid quickly but can't tolerate it. Do not give more solution than your baby would normally drink in a sitting — this will overfill an already irritated tummy and likely cause more vomiting.

After your baby goes for more than about 8 hours without vomiting, restart formula slowly. Start with small, frequent feedings of half an ounce to 1 ounce, or about 20-30 milliliters. Slowly work up to the normal feeding routine. If your infant already eats solids, it's OK to start solid feedings in small amounts again. If your baby doesn't vomit for 24 hours, you can return to your normal feeding routine.

Rehydration Tips: Kids & Teens (Ages 1+)

Give clear liquids (avoid milk and milk products) in small amounts every 15 minutes. The amount you give at one time can range from 2 teaspoons (10 milliliters) to 2 tablespoons (30 milliliters or 1 ounce), depending on the age of your child and how much your child can take without vomiting.

If your child vomits, start over with a smaller amount of fluid (2 teaspoons, or about 10 milliliters) and continue as above. Make sure to avoid straight juices and sodas, both of which could make things worse. Kids may ask for commercial sports drinks, but be careful with these — they have a lot of sugar and could make things worse.

After no vomiting for about 8 hours, introduce solid foods slowly. But do not force any foods. Your child will tell you when he or she is hungry. Your child might want bland foods — saltine crackers, toast, mashed potatoes, mild soups — to start out with.

If there's no vomiting for 24 hours, slowly return to your child's regular diet. There's no need to leave out milk products unless they seem to be making vomiting or diarrhea worse.

Vomiting due to gastroenteritis is caused by viruses that can spread to others. So keep your child home from school or childcare until there's been no vomiting for at least 24 hours. And remember that washing hands well and often is the best way to protect your family against many infections.